Method for transmitting signaling

ABSTRACT

A method for transmitting signaling is proposed which is simple and efficient without taking up significant transmission capacity. In the method, a transmission of the signaling takes place between a mobile station ( 12 ) and a base station ( 11 ) in a mobile radio network. The signaling is transmitted in at least one predetermined time slot ( 301 ), and a different signaling is assigned to each mobile station ( 12 ) disposed in a radio cell of the base station ( 11 ), so that signaling operations of various mobile stations, transmitted via the at least predetermined time slot, can be distinguished from one another in the base station ( 11 ).

BACKGROUND OF THE INVENTION

The invention is based on a method for transmitting signaling.

Methods for transmitting signaling between a mobile station and a basestation in a mobile radio network are already known, for instance fromthe publication entitled “Fast Uplink Signalling Mechanism for FDD andTDD systems”, Tdoc SMG2 UMTS-L1 227/98, Philips Research Laboratories,1998.

SUMMARY OF THE INVENTION

The method according to the invention having the characteristics of themain claim has the advantage over the prior art that the signaling istransmitted in at least one predetermined time slot, and a differentsignaling is assigned to each mobile station disposed in a radio cell ofthe base station, so that signaling operations of various mobilestations transmitted via the at least one predetermined time slot can bedistinguished from one another in the base station. In this way, anunambiguous signaling can be achieved. It is as a rule thereforeunnecessary to repeat the transmission of the signaling. Hence thesignaling leads to the desired outcome especially quickly. This assuresthat the least possible use will be made of transmission resources.Signaling of a plurality of mobile stations is possible by using only asingle joint time slot.

By the provisions recited in the dependent claims, advantageousrefinements of and improvements to the method defined by the main claimare possible.

It is advantageous that each of the mobile stations is assigned its ownsignaling in the form of a different code. Especially in a mobile radionetwork based on code division multiple access with orthogonal codes,this makes it possible to achieve an umambiguous signaling, using theavailable codes, in a simple and efficient way without significantlyclaiming additional transmission resources.

Another advantage is that signaling received in the base station iscorrelated with all the codes assigned to the mobile stations, in orderto ascertain the mobile station associated with the signaling received.In this way, the base station can unambiguously determine the mobilestation that has transmitted the signaling.

It is especially advantageous that the mobile stations are each assigneda time lag by which a predetermined signaling sequence is transmitted indelayed fashion in the at least one predetermined time slot. Thisprovides an alternative possibility of unambiguous, efficient signaling,in which only one time slot and one predetermined signaling sequence arerequired.

Another advantage is that the predetermined signaling sequence istransmitted in spread form by means of a predetermined code. In thisway, transmission of the signaling can be achieved while claimingminimal transmission capacity, especially whenever the predeterminedcode is taken from a set of orthogonal codes, for instance for use in acode division multiple access system.

It is also advantageous that in the base station, on the basis of theamplitude course over time of the received predetermined signalingsequence, the time lag employed is detected in order to ascertain theassigned mobile station. In this way, the base station can unambiguouslydetermine which mobile station sent the signaling.

Another advantage is that the signaling operations are transmitting witha power that is substantially lower than the power for transmittinguseful data. In this way, the additional interference caused by thesignaling is minimized.

It is also advantageous that at least one of the signaling operations istransmitted together with another signaling or with useful data of analready existing connection in the at least one predetermined time slot.This economizes on transmission capacity.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the invention are shown in the drawing andexplained in further detail in the ensuing description.

FIG. 1 shows a mobile radio network in simplified form;

FIG. 2 shows the layout of a burst for a transmission in a time divisionduplex operating mode;

FIG. 3 shows the layout of a transmission frame in the time divisionduplex operating mode; and

FIG. 4 shows a code tree for generating a code.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In a mobile radio network 10, which can for instance be embodied by theGSM standard (Global System for Mobile Communication) or the UMTSstandard (Universal Mobile Telecommunications System), not only theuseful data, which are present for instance in the form of speechsignals, but also signaling data, for instance for hand-over proceduresor for setting up new channels must be transmitted both in a downlinktransmission direction 13 from a stationary base station 11 to a mobilestation 12 as in FIG. 1 but also in an uplink transmission direction 14from the mobile station 12 to the base station 11. The invention will bedescribed below in terms of a mobile radio network, as an example on thebasis of a mobile radio network 10 by the UMTS standard, which willhereinafter be called a UMTS mobile radio network 10.

In the UMTS mobile radio network 10, two modes for transmission by wayof the air interface are provided: In an FDD mode (Frequency DivisionDuplex), two different frequencies exist for the uplink transmissiondirection 14 and the downlink transmission direction 13. In a TDD mode(Time Division Duplex), only a single carrier frequency is used for bothtransmission directions, and by the allocation of time slots aseparation between the downlink transmission direction 13 and the uplinktransmission direction 14 is made.

The signals of various subscribers of the mobile radio network areseparated from one another by spreading using orthogonal codes. In theTDD mode, the thus-spread signals of the various subscribers aretransmitted within the same time slot.

It will be assumed as an example below that the UMTS mobile radionetwork 10, shown in simplified form in FIG. 1, is embodied by the TDDmode. FIG. 3 shows the layout of a transmission frame 30 used for thepurpose. Each transmission frame, in this example, has a chronologicallength of 10 ms and comprises a total of fifteen time slots 301, 302, .. . , 315. A first time slot 301 is to be reserved for transmission inthe uplink transmission direction 14, and a second time slot 303 is tobe reserved for transmission in the downlink transmission direction 13.Within each of the time slots 301, 302, . . . , 315, precisely oneso-called TDD burst 20 as in FIG. 2 can be transmitted. This burstcomprises two data blocks 21, 23 for data transmission, a midamble block22 for channel estimation, and a protective spacing 24.

Within each of the time slots 301, 302, . . . , 315, useful data from amaximum of sixteen subscribers can be transmitted, on the principles ofa CDMA system (Code Division Multiple Access). To achieve this, theuseful data to be transmitted from the various subscribers must bespread in the applicable time slot before being transmitted. In FIG. 4,a code tree is shown, with the aid of which so-called OVSF (OrthogonalVariable Spreading Factor) codes are created for spreading the usefuldata to be transmitted.

Along with the useful data, signaling operations are also transmittedbetween the mobile station 12 and the base station 11. These signalingoperations can serve for instance to request a transmission channel,send a command for regulating the transmission power, or transmit areference signal for a channel estimation. In all these cases named, areaction to the signaling is to be brought about in the station thatreceives the signaling. This reaction, for the cases cited as examples,then comprises either the allocation of a transmission channel, theadjustment of the transmission power, or the estimation of the channelpulse response on the basis of the reference signal received, forinstance for use for a predistortion by a JP (Joint Predistortion)process. Below, how such signaling operations are transmitted from themobile station 12 to the base station 11 will be described, taking as anexample signaling for requesting a transmission channel.

In a first exemplary embodiment, the signaling operations are generatedfrom the OVSF codes described. The code tree shown in FIG. 4 illustratesthe generation of the OVSF codes up to a spread factor SF=8. In the TDDof the UMTS mobile radio network 10, OVSF codes with spread factorsSFε{1,2,4,8,16} are currently possible. With the aid of the OVSF codes,orthogonal code sequences can be generated, and an essential property isthat codes of different length are also orthogonal to one another.

In this first exemplary embodiment, transmission of the signalingoperations is meant to be possible only in the first time slot 301.Within the first time slot 301, all the signaling operations aregenerated from a certain, previously defined spreading code of length16, where the spread factor SF is thus 16. For instance, the lastspreading code with the spread factor SF=16 selected, which in FIG. 4,where the code tree is shown up to the spread factor SF=8, would belocated at the lowermost point if continued appropriately. Thislowermost branch of the code tree with the spread factor SF=16 is nowexpanded up to the spread factor or length of 256. Thus within the firsttime slot 301, a total of sixteen codes are available for the signaling.In other words, sixteen codes with a spread factor of 256 of the OVSFcodes are used for the signaling.

With these codes of length 256 for the signaling, only one signalingburst is now constructed, which has the same structure as the TDD burst20 shown in FIG. 2. The code for the signaling is repeated within thedata blocks 21, 23 until such time as these blocks are filled; the codefor the signaling can be cut off at the last required repetition forfilling up the data blocks 21, 23. In the first time slot 301, themidamble block 22 is also allocated to each such TDD burst 20 embodiedas a signaling burst.

Among the codes described for signaling, the code that would be locatedat the very bottom in the code tree of FIG. 4, with the spread factorSF=256, is allocated or assigned to the mobile station 12, for instanceat the time of check-in into the radio cell of the base station 11. Itcould additionally be agreed that the mobile station 12 has completeauthority for signaling. Then mobile stations without authority forsignaling are not allocated any codes for signaling. Each mobile stationauthorized for signaling is assigned a different code for signaling. Ifthe mobile station 12 requires only one channel for useful datatransmission in the uplink transmission direction 14, hereinafter calledthe uplink channel, then in the first time slot 301, it sends itsallocated code for signaling in order to request such a channel,whereupon the base station 11 informs the mobile station 12 of theparameters for such an uplink channel in the second time slot 303. Theallocated uplink channel can also be located in the first time slot 301,so that in the subsequent transmission frame 30 the mobile station 12can likewise begin to transmit the useful data in the first time slot301.

The transmission power of the signaling burst 20 is substantially belowthe transmission power of a normal burst for transmitting useful data.Thus the additional interference in the uplink transmission direction14, caused by the use of the signaling burst 20, is minimal. Detectingthe signaling code, received in the base station 11, and thus detectingthe mobile station 12 assigned to this signaling, is done by correlationwith the sixteen different predetermined codes for signaling.Alternatively, the signaling codes can be detected by a JD (JointDetection) process.

In the event that the sixteen predetermined codes for signaling in thefirst time slot 301, as the sole time slot used for signaling pertransmission frame 30, are too few, the transmission of the signalingcould be expanded to additional time slots in the uplink transmissiondirection 14. It would also be conceivable to increase the number ofpredetermined codes for signaling, by using even higher spread factorsthan 256 in the code tree for generating these signaling codes. Forinstance, if an expansion to the spread factor SF=1024 is accomplished,a total of sixty-four codes for signaling are available.

In a second exemplary embodiment, the signaling can be performed instill another way. In the first exemplary embodiment, the OVSF codes areused directly as codes for signaling. In the second exemplaryembodiment, although once again a specific OVSF code with the spreadfactor SF=16 is now to be reserved again for the signaling, for instancethe lowermost code in the code tree having the spread factor SF=16.However, this code is used for spreading a signaling sequence that ispredetermined for all the mobile stations in the radio cell of the basestation 11 that are authorized for the signaling. This signalingsequence is a fixed symbol sequence, identical for all the mobilestations authorized for signaling in the radio cell of the base station11, with good autocorrelation properties. The signaling sequence isspread with the OVSF code predetermined or reserved for the purpose andis transmitted in the data blocks 21 and 23 of the signaling burst 20.The signaling sequence should comprise enough symbols that, being spreadwith the spread factor SF=16, it lasts precisely as long as the two datablocks 21 and 23 together. Each mobile station that uses this signalingsequence is allocated a different time lag for starting the signalingsequence. The mobile station 12 begins with the start of the signalingsequence exactly at the time of the start of the signaling burst 20,shown in FIG. 2 and used for the signaling. A second mobile station, notshown, in the radio cell of the base station 11 begins with its start ofthe signaling sequence four symbols later, for instance. This isequivalent to a time lag of sixty-four chips. Since the signalingsequence however contains four symbols more than can be transmitted,beginning with the aforementioned time lag, in the data blocks 21, 23,the remaining four symbols are transmitted at the beginning of thesignaling burst 20. The signaling sequence is accordingly transmitted,cyclically delayed, for different mobile stations, and each time lagunambiguously identifies the mobile station 12 associated with this timelag. The time lag for the various mobile stations comprises multiples offour symbols, that is, multiples of sixty-four chips after spreading bythe spread factor SF=16. This value of four symbols is equivalent to amaximum incident length of the transmission channel of sixty-four chips.The result is thirty possible different time lags, or thirty differentmobile stations, per time slot used for the signaling in the uplinktransmission direction 14. The cyclically delayed signaling sequence isthen further spread with the predetermined OVSF code described, so thatthe orthogonality relative to the other signals transmitted in the sametime slot will be assured. Once again, each signaling burst 20 isallocated its own midamble block 22.

The transmission power of this signaling burst 20 is once again very lowin comparison with useful data bursts. The detection of the signalingbursts 20 received in the base station 11 is effected after theunspreading, for instance by means of a matched filter with peakdetection. Depending on the point in time in the amplitude course of thereceived and unspread signaling burst 20 when a maximum value occurs, aconclusion can be drawn as the fundamental time lag and the transmittingmobile station associated with it, and accordingly the construction ofan uplink channel requested by the signaling can be initiated. Theunspreading of the signaling burst can also be performed a JD process.

In both exemplary embodiments, the signaling can be detected especiallyquickly, if the transmission quality allows this: If the detectionquality within the first data block 21 is already sufficient to make areliable decision, then the evaluation of the second data block 23 canbe dispensed with.

In a further embodiment, it can additionally be provided that the spreadsignaling sequence be transmitted in only one of the two data blocks 21,23. To that end, in comparison with the embodiment described above, thesignaling sequence is divided in half in terms of its length. Thus thevarious mobile stations can additionally be distinguished from oneanother in the base station 11 according to which of the two data blocks21, 23 the signaling sequence was transmitted in and was received in thebase station 11.

Because of the rigid dividing up of the time slots to the differenttransmission directions, namely the downlink transmission direction 13or the uplink transmission direction 14, the advantage of fastsignaling, for instance in the uplink transmission direction 14, canunder some circumstances be limited, especially if only one time slot inthe uplink transmission direction 14 per transmission frame 30 isallocated.

This can be counteracted by providing that the transmission of thesignaling, in the first or second exemplary embodiment, in the uplinktransmission direction 14 is also made possible by using a time slot inthe downlink transmission direction 13. In general, the signaling can betransmitted together with another signaling or with useful data of analready existing connection, within a joint time slot.

Because of the low transmission power provided for transmitting thesignaling burst 20, only slight additional interference need beexpected. However, both in the first and the second exemplaryembodiment, it must be assured that the spreading code reserved fortransmitting the signaling, having the spread factor SF=16, not be usedin the downlink transmission direction 13.

The use of a joint time slot for signaling as described forms its ownsignaling channel, which is also known as a FAUSCH (Fast UplinkSignaling CHannel) for the uplink transmission direction 14. Althoughwith the FAUSCH a new channel is introduced in the uplink transmissiondirection 14, still the required changes in the mobile station 12 andthe base station 11 are only slight.

An advantage of the method of the invention is the capability of themobile station 12, in the TDD mode, of transmitting a 1-bit signaling,for instance, without a time lag in the intended or predetermined jointfirst time slot 301 to the base station 11; in the base station 11, thesignaling then leads to a previously defined reaction and at the sametime does not represent any significant worsening of other channels.

1. A method for transmitting signaling from a mobile station to a basestation in a mobile radio network, comprising the following steps:transmitting the signaling in a common, predetermined time slot sharedby a plurality of mobile stations; assigning each mobile stationdisposed in a radio cell of the base station a different signaling inthe form of a different code, so that signaling operations of variousmobile stations transmitted via the at least one predetermined time slotare distinguished from one another in the base station.
 2. The method ofclaim 1, wherein each of the mobile stations (12) is assigned its ownsignaling in the form of a different code.
 3. The method of claim 2,wherein on the basis of a predetermined spreading code of predeterminedlength, the different signaling operations are generated in that thepredetermined spreading code is expanded in its length in order tobranch out into a plurality of codes, in particular orthogonal codes. 4.The method of claim 3, wherein a signaling received in the base station(11) is correlated with all the codes assigned to the mobile stations,in order to ascertain the mobile station associated with the signalingreceived.
 5. The method of claim 1, wherein with the signaling, areference signal for a channel estimation is transmitted.
 6. The methodof claim 1, wherein the predetermined signaling sequence is transmittedin spread form by means of a predetermined code.
 7. The method of claim1, wherein in the base station, on the basis of the amplitude courseover time of the received predetermined signaling sequence, the time lagemployed is detected in order to ascertain the assigned mobile station.8. The method of claim 6, wherein the spread signaling sequence istransmitted in only one of two data blocks (21, 23) of a burst (20)disposed in the at least one predetermined time slot (301).
 9. Themethod of claim 8, wherein in the base station (11), the particular oneof the two data blocks (21, 23) in which the signaling sequence has beentransmitted is detected, in order to ascertain the assigned mobilestation.
 10. The method of claim 1, wherein the signaling operations aretransmitting with a power that is substantially lower than the power fortransmitting useful data.
 11. The method of claim 1, wherein at leastone of the signaling operations is transmitted together with anothersignaling or with useful data of an already existing connection in theat least one predetermined time slot (301).
 12. The method of claim 1,wherein the mobile radio network is operated by a CDMA-TDD process(CDMA=Code Division Multiple Access; TDD=Time Division Duplex), usingorthogonal codes.
 13. The method of claim 1, wherein with the signaling,a request for a transmission channel for setting up a connection betweenthe mobile station (12) and the base station (11) is transmitted. 14.The method of claim 1, wherein with the signaling, a command forregulating the transmission power is transmitted.
 15. A method fortransmitting signaling from a mobile station to a base station in amobile radio network, comprising the following steps: transmitting thesignaling in at least one predetermined time slot shared by a pluralityof mobile stations; assigning each mobile station disposed in a radiocell of the base station a different signaling, wherein the mobilestations are each assigned a time lag; transmitting a predeterminedsignaling sequence in delayed fashion according to the time lag in theat least one predetermined time slot, so that signaling operations ofvarious mobile stations transmitted via the at least one predeterminedtime slot are distinguished form one another in the base station.
 16. Amethod for transmitting signaling from a mobile station to a basestation in a mobile radio network, comprising the following steps:transmitting the signaling in at least one predetermined time slotshared by a plurality of mobile stations; assigning each mobile stationdisposed in a radio cell of the base station a different signaling,wherein the mobile stations are each assigned a time lag; transmittingcyclically delayed a predetermined signaling sequence in the at leastone predetermined time slot, whereby the symbols of the signalingsequence that is be transmitted in the at least one predetermined timeslot, beginning with said time lag, a beginning of the at least onepredetermined time slot, so that signaling operations of various mobilestations transmitted via the at least one predetermined time slot aredistinguished from one another in the base station.